Apparatus for the manufacture of organic compounds



Dec. 14, 1954 APPARATUS FOR THE MANUFACTURE OF' ORGANIC COMPOUNDS Lsl T. B. HAUFE El' AL original Filed Feb. 26, 1949 United States Patent APPARATUS FOR THE MANUFACTURE OF ORGANIC COMPOUNDS Ted B. Haufe, Western Springs, and John 0. Iverson,

Chicago, Ill., assignors to Universal Oil Products Company, Chicago, Ill., `a corporation of Delaware Original application February 26, 1949, Serial No. 78,588, now Patent No. 2,631,161, dated March 10, 1953. Divided and this application May 23, 1952, Serial No.

5 Claims. (Cl. 23-260) This reaction takes place spontaneously when methanol and phosphorus trichloride are mixed. The reaction is exothermic to the extent of about 32 kcal. per mole of phosphorus trichloride (420 B. t. u./lb.) on the basis of phosphorus trichloride, methanol and dimethyl hydrogen phosphite being liquids and of methyl chloride and hydrogen chloride being present as gases. Actually at least one-half of the hydrogen chloride remains in the liquid product, at least partially in chemical combination with the dimethyl hydrogen phosphite. Under thesevcircumstances the actual heat of reaction is from 50 to 100% greater than that mentioned above. In order to control the reaction, cooling of the reaction mixture is obtained by recycling liquid methyl chloride so that about 5 to about l moles of liquid methyl chloride is admixed with one mole of phosphorus trichloride charged to the process or on a weight basis this corresponds to about 2.5 to about pounds of liquid methyl chloride per pound of phosphorus trichloride.

The process and apparatus for effecting the production of dimethyl hydrogen phosphite'is set forth and illustrated in more detail hereinafter, and includes the following improvementsand refinements in design over those used heretofore.

- (l) Precooling of the reactants to reaction temperatures of from about 30 to about +10 C. in external coolers. t

(2) Mixing of phosphorus trichloride and methyl chloride and contacting the mixture with methanol in a jet type mixer with a minimum of residence time between intimate contacting of reactants and separation of hydrogen chloride product from the liquid reaction products.

(3) Operation of the degassing or stripping column at essentially the same pressure as the reactor by providing sutiicient -methyl chloride stripping vapors to maintain the partial pressure of hydrogen chloride at less than that in the low pressure degassing column used heretofore. (4) Addition of a fractionation section, above the stripping section, which is reiluxed with liquid methyl chloride to insure complete removal ofdmethyl hydrogenphosphite from the hydrogen chloride-methyl chloride vapors leaving the column. l (5) Substitution of high pressure fractionation system for separation and recovery of hydrogen chloride and methyl chloride in the anhydrous state in place of a water absorption system as used heretofore. V(6) Preheating and vaporization of the dimethyl hyldrogen phosphite in the charge'to the distillation rerun column with addition of a stripping section for countercurrenty stripping of the bottoms product with methyl chloride vaporsv to improve the recovery of dimethyl hydrogen phosphite from the bottoms product. f f

One embodiment of the means forelecting the reaction between phosphorus trichloride and methanol in producing dimethyl hydrogen phosphite comprises in combination, an elongated reactor-stripping chamber having upper and lower packed sections, a reactant stream ow mixer connecting to the side of the said chamber and discharging into a vapor disengaging section positioned between the upper and lower packed sections of the chamber, a plurality of stripping liuid inlets connecting with the lower portion of the chamber and discharging into said lower packed sections at vertically spaced levels therein, whereby methyl chloride may be injected into the presence of the resulting product stream ilowing down through the chamber and prevent any undesired side reaction between the resulting dimethyl hydrogen phosphite and hydrogen chloride, heating means connecting with the lower portion of the chamber suitable to provide for the vaporizing of the methyl chloride, a reiiux stream inlet connecting with the upper portion of the chamber whereby methyl chloride may also be used to remove entrained dimethyl hydrogen phosphite from the overhead vapor stream, and

and lower ends of the said reactor-stripping chamber.

tion is illustrated diagrammatically by the attached drawing which shows in general side elevation a combination of equipment suitable for effecting the process. In accordance with the means illustrated in the drawing, methanol is introduced through line 1 to pump 2 which discharges through line 3 and valve 4 into cooling coil 5 which is disposed in reactant cooler 6 in which liqueed methyl chloride, recovered as hereinafter set forth, is permitted to vaporize. The cooled methanol is then directed from coil 5, through line 7, to reactor mixer 17. Also from another outside source, phosphorus trichloride is directed through line 8, pump 9, which discharges through line 10 and valve 11 to iilter 12, from which the phosphorus trichloride is directed through line 13, to cooling coil 14, which is also disposed in reactant cooler 6. From cooling coil 14, the cooled stream of phosphorus trichloride is discharged therefrom through line 15 into line 16 where it is diluted with liquid methyl chloride introduced as hereinafter set forth.

The precooled stream of methanol being introduced through line 7 and the. precooled mixture of phosphorus trichloride and methyl chloride are commingled rapidly in reactant mixer 17 in which the heat of reaction at the point of contact is highly exothermic and is estimated to be about 630 B. t. u./ lb. of phosphorus trichloride charged. The heat of reactionis removed by vaporization of the methyl chloride from the reaction mixture. The methyl chloride required for removing this quantity of heat and maintaining the reaction mixture ata temperature of from 30 to about 10 C. or preferably at 20 to 0 C. or lower is mixed with the phosphorus trichloride charged prior to contact with methanol in order to insure adequate cooling without localized overheating in the reaction zone. The reactor mixer 17 must be so designed as to provide suflicient pressure drop and turbulence in the mixing zone to eiect an intimate contact of the phosphorus trichloride and methanol immediately prior to discharge vof the efiluent into reactor stripper 18 in the vapor disengaging space provided between a lower bed and an upper bed of carbon Raschig rings. For example, in a reactor stripper 44 feet long and of 4.5 feet internal diameter, the lower bed of carbon Raschig rings is 20 feet thick and the upper bed is 10 feet in thickness.

In some cases mixer 17 may not be used but the reactants may be commingled in the vapor disengaging space in reactor stripper 18.

The reaction between the methanol and phosphorus trichloride to produce dimethyl hydrogen phosphite is completed in the reactor-stripper while the liquid passes downward through the stripping section of the reactorstripper column 18 countercurrent to methyl -chloride vapors generated in the reboiler or introduced from the reactant cooler 6 by Way of line 31, valve 32, line 33, and valve 34. A portion of the methyl chloride may be introduced as liquid from reactant cooler 6 by way of line product outlets from both the upper tion of the methyl chloride being discharged to header Z is directed therefrom through line 16- already mentioned containing valve 26. Reactor-stripper 18 may also be operated sometimes Without adding methyl chloride through lines 20, 22and24i asindicated'abovet.

The.y reactor stripper is. designed for operation at'. ant absolute pressure of aboutv 350 mms, of` mercury. instead. of. at a pressure of aboutSO mm. of mercury as employed heretofore.. This increase in the mentioned: operating pressure-iscompensated for by increasing the quantity ofrnethyl chloride stripping vapors, thereby loweringthe partial pressure of hydrogen chloride inthe mixture, andi accordingly decreasingvthe tendency of the dimethyl hy.- drogen phosphite toreact further withshydrogen. chlorideto. produce additional methyl chloridefat. the. expense of; thedesired. dimethyl hydrogen phosphite.. The; temperaf tureof the lower sectlonf ofthe reactor-stripper column may be controlled' by, varying: the amount: of. methyl chloride introducedby lines 20,` 22. and 24 intothenliquid` mixture and passing.V downwardly. through. the column. The" hydrogen chloride: which is stripped from the dimethyl hydrogen phosphite and higher boiling products in reactor stripper 18 and also. they methyl chloride: are directed. fromfthe top-of. reactor stripper 1S through line. 27; containing valve 28 toy further compressiomliquefaction,. and` fractional distillation as hereinafter set7 forth. The.V reactor-stripper. column ispreferably provided with aI reflux; of liquid; methyl chloride. which is introduced fromline through line-29.1andrvalve.3010 near the top of: the fractionator 18 already mentioned toimaintain a temperature therein of about -459 C. in order to insure. substantially complete removal of'the'entrained` dimethyl hydrogen phosphite from the overheadvapors passing to thecompressors. As a; mixture of dimethyl.v hydrogen phosphite and hydrogen chloride is extremely. corrosive, the complete removal of dimethyl. hydrogen phosphite is essentialy for satisfactory operation of the compressor system.

The costl` of plant construction may be lowered considerably by increasing the operating. pressure of the re actor-stripperv column. Fory example,- onc stage of the usual three-stage compressor system could be eliminated if the pressure in the column is increased to approximately 1.3 atmospheres absolute. The operating pressure in the reactor-stripper is generally fromabout 0.25 to about 3.0 atmospheres. The costi of the alloy lined columncanalsobe reduced when the operating pressure isincreased and the operationcan be simplified in gen-l eral by operating at slightly above atmospheric pressure;

Thetemperature can still be maintained in the desired low range by increasing chloride in the mixture.

As already indicated, the charged methanoland phosphorus trichloride are precooled by indirect heat exchange with vaporizing methyl chloride in reactant cooler 6. The-vapors so produced are directed from cooler 6, through line 31 and .valve'32 and atleast aportion there-v of'is conducted through branch line 33 containing valve 34. to near the bottom of reactorstripper 18tand utilized therein as astripping agent for removing hydrogen chloride from the reaction mixturey present therein. The stripping isthus improved by introducing methyl chlo ride which is free from hydrogen chloride as stripping vapors at the bottom of column 18,

From the bottom of reactor-stripper. 18, the mixture-of dimethyl hydrogen phosphite and higher boiling products is conducted through line 35i to pump 36,.which discharges through line 37, heat exchanger 38; andline 39, into reruncolumn 40. Heat'may be addedto the bottom of reactor-stripper 18 by means of steam or other heating medium` circulated through reboiler coil- 41. Alternatively, a portion of the material being discharged through line 35 may be passed through an external reboiler coil, not shown in the drawing, and be-returned to the bottoni of reactor-stripper 18.

Rerun column 40 may be a vertical cylindrical vessel provided with a plurality of perforated plates or decks to assist in the fractional distillation.` For example, a rerun column with aninside diameter ot`13.5v feet'anda length-of 44 feet is provided with 25 decks arrangedwith a 1.5 foot space between decks. This rerun,l column is designed for fractionally'distilling-andLseparating the dimethyl hydrogen phosphiteV from higher boil-ing byproducts. The maximum temperature allowable to avoid decomposition of the heavyby-prodtletsL is` about the concentration of methyl 150 C. and therefore the process temperature in rerun column 40 isgener-allyl limitedtoY 140 C., with` 150 C. on the hot side of the heat exchanger surface. The charge to rerun column is preheated by heat exn changer 38 to a temperature of 140 C. at an absolute pressure of 50 mm. of mercury,y a superheat of approximately 5.0" C. onthedimethyl hydrogen phosphitevapors, in order'to supply. sui'cient'heat. to column 40-to effect the desired fractionation; The non-vaporized by-products pass downwardly countercurrent. to.- methylf. chloride vapors, introduced. atthe bottom. ofthe column by conducting methyl chloride frorn line 311 already mentioned, through branch line 4Z, valve 43, heat exchanger 44 and line 45 to thebottom ofrcolumny 40. This. strippingof thehigh-boiling byaproductsin column140 with methyl chloride vapors, improves the recovery of dimethyl hydrogen phosphite from said high-boiling by-products. Column 40 may also be equipped with bubble decks in order to provide'suilicient vapor-liquid' contact. For this purpose, low pressure decks. are preferred to: avoid; extensive pressure drop through thev column. From the top. of rerun column 40, the dimethyl hydrogen phosphite and small amounts of methyll chloride contained therein. are passed through line 46 cooler. 47,. from which the liqueed dimethyl hydrogen phosphite'` and noncondensedy vapors are. directed' through` line 48 to receiver 49. The non-condensed vapors from receiver 49 are directedI through line 50to.fvacuumvpump 51l which discharges.y saidvapors through line 52 and: thence byV way of line 33 intostrippery 18; alreadyv described. The vaporsso returned through linesSZ and 33 to stripper 18 contain about l5 Wt. per cent of dimethyl hydrogen phosphite.

Dimethyl hydrogen phosphite collected.. in receiver 49 is withdrawn. therefrom through line 53 bypump 54 which discharges through line 55 into line: 56 contains ing valve 5.7: from which the dimethyl hydrogen-phosphite is directed to storage not indicated in the diagrammatic drawing. A portion of the dimethyl hydrogen phosphite being'discharged by pump 54A through line 55 isthereby conducted to near the top of reruny column 40to act.` as reflux liquid. and to assist in controllingthe temperature and.V fractionation therein. From the bottom; of rerun column 40, the high-boiling by-products, boiling higher than. dimethyl hydrogen phosphite, are withdrawn throughline 58, cooler 59, andvalve to waste storage orotherfuse not indicated in thediagrammatic draw.-

ing..

As an` alternative, to theaboveaindicated methodof operatingtrerun columnV 40, it is'also sometimes desirable to use a naphtha fraction or other materialiwith a boiling. range higher. than that ofy the dimethyl hydrogen phosphite as a meansof. supplying heat'and'to serve asza stripping medium. in this rerun column.. With this use of: naphtha,l it wouldnot benecessary tovadmit methyl chloride vapors through lines 42 and 45, but the naphtha couldbe charged to rerun` column 10 by means not indicated;k in the attached. diagrammatic. drawing. With such a method of operation, the vapors taken overhead from the.ftop.of;the. reruncolumn'couldthen all be condensed and thusl decrease the requiredfcapacity'of the vacuum pump to -beemployed: The .bulk'of the'naphtha couldibe retained in the column, thev column couldl be reboiled vby adding: sufficient. heat-.by heat .exchanger 44 or by otherfmeans notillustrated in the: drawing, and thesmall amount.1 of naphtha removedwiththe voverhead vapors or. with' the higher.' boiling: material withdrawn from t the bottom e of the.; column could be; recovered i as a separatezlayer for.` returnto-the rerun column. Suchaa methodof operationwouldzpermit ther use ofza higher column pressure: in therange of. from1ab'out'50'mm; of mercury tol one. atmosphere. absolute: (760! mm.)- with its resultant'saving.- in cost?. ofplanty and operation.:

The mixture of hydrogen chloride andmethyl' chloridel separated* as hereinbeforefset forth in stripper 18 and directed therefrom through line 2.?7-"and'fvalvev ZStis passed through heat exchanger'61 through lwhich' steam =or some other heatingmediuml iscirculatedzto insure va porizationv ofv the mixture of` hydrogen? chloride 1 and methyl chloride'y Whichtis'conductedithrough line 62 to suction tank 63` connected by 'line f 614iy to compressor 65 which dischargesfthrough:line 66 into'fcooler 67ffrom which they lique'ed mixture of methyl 'f' chloride and'Y hy`- drogen chloride'lis `conductedithrough line:A 681 to receiving: tank 691. While-only one-'stageof i a-fcompressor f system for the hydrogen chloride-methyl chloride mixture is shown in the attached diagrammatic drawing, a multiple-stage compressor system may also be employed, for example, a three-stage compressor system, in order to produce a liqueiied mixture of hydrogen chloride and methyl chloride.

From receiver 69, the liquefied mixture of hydrogen chloride and methyl chloride is withdrawn through line 70 by pump 71, which discharges through line 72 and valve 73 into fractionator 74 of suitable design such as a vertical cylindrical vessel packed with one or more beds or sections of carbon Raschig rings or other suitable tower packing material. For example, the vapors discharged from compressor 65 are condensed in a watercooled condenser such as condenser 67 and then directed through line 68 to receiver 69 from which the condensate is pumped through line 70 by pump 71 and discharged through line 72 and valve 73 into fractionator 74 operated at an absolute pressure of 25 atmospheres, and in which the hydrogen chloride vapors are separated from methyl chloride. The hydrogen chloride so separated is discharged from the top of fractionator 74 through line 75 and valve 76 to storage or to other use not indicated in the diagrammatic drawing. The top of fractionator 74 is provided with liquid reflux by directing the vapors from the top of fractionator 74 through line 77 to heat exchanger 78 which is refrigerated by means of methyl chloride recovered in the process and directed to and away from heat exchanger 78 by lines 79 and 80, respectively. From heat exchanger 78, the retiux condensate formed therein from the vapors in troduced through line 77 is discharged through line 81 into the top of fractionator 74. If desired, the top ot fractionator 74 may be cooled sufficiently to remove the hydrogen chloride stream as a liquid through line 75 and valve 76.

From the bottom of fractionator 74, the methyl chloride is removed as a liquid through line 83, passed through cooler 84, and through lines 85 and 86 to receiver S7. Also a portion of the methyl chloride which is being withdrawn through line 83 may be directed therefrom through line 88, heat exchanger 89, and be returned through line 9i) to the bottom of fractionator 74 to supply heat thereto and serve as a reboiler means. Vapors of methyl chloride present in receiver 87 may be discharged therefrom through line 31 and directed therefrom through line 33 and valve 34 already mentioned to the bottom of reactor stripper 18 to assist in the separation of hydrogen chloride from the reaction products. A portion of the liquid methyl chloride is directed from receiver 87 through line 79 already mentioned, containing valve 91 to heat exchanger 78 maintained, for example, at a temperature of about -18 C. as hereinbefore set forth. From heat exchanger 78 vaporized methyl chloride is conducted through line 80 to suction tank 92 and from thence by line 93 to refrigeration compressor 94 which discharges through line 95 into cooler 96 in which the compressed methyl chloride vapors are liqueed and the resultant liquid methyl chloride is conducted from condenser 96 through line 86, already mentioned, to receiver 87. Some of the liquid methyl chloride contained in receiver 87 is withdrawn therefrom through line 97 and valve 98 to storage, while another portion of the liquid methyl chloride being directed through line 97 is conducted therefrom through 6 line 99, containing valve 100, and recycled to cooler 6 employed for precooling the charged methanol and phosphorus trichloride by indirect heat exchange with vaporizing methyl chloride as hereinbefore set forth.

It may be noted, however, that the drawing and the foregoing described embodiment are merely illustrative and that minor modifications or substitutions in design and construction may be made within the scope of the present invention. For example, suitable contact decks such as bubble trays or side-to-side pans may well be used within the upper and lower contacting sections of the reactor stripping column 18 in place of the Raschig rings or other packing material. Also, in some instances it may be desirable to utilize a packing material with the rerun column 40 instead of the perforated plates or decks which have been described and shown in connection with the present embodiment. The drawing also indicates a multi orice ilow mixing means 1'7 connecting with and discharging into the central vapor disengaging space of the reactor-stripping column 19, however, it is not intended to limit the unitary apparatus to the use of any one specific typeof orice or iow mixing means, as long as such mixing means may be directly adjacent to and attached with the column in a manner discharging an intimately mixed reaction stream -directly into the middle portion of the column.

We claim as our invention:

' l. An apparatus of the class described comprising a vertical chamber having upper and lower packed sections, a reactant stream flow mixer connected to the chamber and discharging into a vapor disengaging space between said packed sections, a vaporizing chamber and means for introducing thereto a liquid to be vaporized, a pair of reactant cooling coils disposed within said vaporizing chamber and connected with said mixer, means for passing vapors from the vaporizing chamber into the lower portion of said vertical chamber, and outlet means at the upper and lower ends of the last-named chamber.

2. The apparatus of claim l further characterized in the provision of means for passing liquid from said vaporizing chamber into said vertical chamber.

3. The apparatus of claim l further characterized in the provision of means for passing liquid from said vaporizing chamber into the upper portion of said vertical chamber.

4. The apparatus of claim l further characterized in the provision of means for passing liquid from said vaporizing chamber into said vertical chamber at vertically spaced points in the height thereof. 5. The apparatus of claim 1 further characterized 1n the provision of means for passing liquid from said vaporizing chamber into the lower packed section of said vertical chamber.

References Cited in the ile of this patent UNITED STATES PATENTS Number Name Date 2,081,322 Carney May 25, 1937 2,224,925 Potts et al. Dec. 17, 1940 2,332,493 Petry et al. Oct. 19, 1943 2,371,477 Sonders, Jr. et al Mar. 13, 1945 2,433,060 Ohsol et al Dec. 23, 1947 2,582,817 Chadwick Jan. 15, 1952 

1. AN APPARATUS OF THE CLASS DESCRIBED COMPRISING A VERTICAL CHAMBER HAVING UPPER AND LOWER PACKED SECTIONS, A REACTANT STREAM FLOW MIXER CONNECTED TO THE CHAMBER AND DISCHARGING INTO A VAPOR DISENGAGING SPACE BETWEEN SAID PACKED SECTIONS, A VAPROIZING CHAMBER AND MEANS FOR INTRODUCING THERETO A LIQUID TO BE VAPORIZED, A PAIR OF REACTANT COOLING COILS DISPOSED WITHIN SAID VAPORIZING CHAMBER AND CONNECTED WITH SAID MIXER, MEANS FOR PASSING VAPORS FROM THE VAPORIZING CHAMBER INTO THE LOWER PORTION OF SAID VERTICAL CHAMBER, AND OUTLET MEANS AT THE UPPER AND LOWER ENDS OF THE LAST-NAMED CHAMBER. 